Standardize usage of virtual/override/final in chrome/browser/extensions/

chrome/browser/extensions/api/audio/audio_service.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/audio/audio_service.h"
 
 namespace extensions {
 
 class AudioServiceImpl : public AudioService {
  public:
   AudioServiceImpl() {}
-  virtual ~AudioServiceImpl() {}
+  ~AudioServiceImpl() override {}
 
   // Called by listeners to this service to add/remove themselves as observers.
-  virtual void AddObserver(Observer* observer) override;
-  virtual void RemoveObserver(Observer* observer) override;
+  void AddObserver(Observer* observer) override;
+  void RemoveObserver(Observer* observer) override;
 
   // Start to query audio device information.
-  virtual void StartGetInfo(const GetInfoCallback& callback) override;
-  virtual void SetActiveDevices(const DeviceIdList& device_list) override;
-  virtual bool SetDeviceProperties(const std::string& device_id,
-                                   bool muted,
-                                   int volume,
-                                   int gain) override;
+  void StartGetInfo(const GetInfoCallback& callback) override;
+  void SetActiveDevices(const DeviceIdList& device_list) override;
+  bool SetDeviceProperties(const std::string& device_id,
+                           bool muted,
+                           int volume,
+                           int gain) override;
 };
 
 void AudioServiceImpl::AddObserver(Observer* observer) {
   // TODO: implement this for platforms other than Chrome OS.
 }
 
 void AudioServiceImpl::RemoveObserver(Observer* observer) {
   // TODO: implement this for platforms other than Chrome OS.
 }
 
@@ skipping 11 matching lines @@
 }
 
 bool AudioServiceImpl::SetDeviceProperties(const std::string& device_id,
                                            bool muted,
                                            int volume,
                                            int gain) {
   return false;
 }
 
 }  // namespace extensions